“We were just really excited to have Marg come back because, obviously, she’s such an important part of the history of CSI,” executive producer Don McGill shares. “And she was super excited. It was kismet!”

The milestone hour, airing later this fall, centers on a fictional cold case, one that “takes our characters back to the beginning,” McGill reveals. “They have to investigate a murder with the same M.O. and the same suspect from 14 years ago.”

Helgenberger’s return comes partly via a series of recreated flashbacks, or “faux-backs,” as McGill calls them. Explains the EP: “We will flash back 14 years to seminal moments that show Catherine, Nick (George Eads), Sara (Jorja Fox), Greg (Eric Szmanda) and Ecklie (Marc Vann) as they were, [and how that] informed the evolution of the characters now. It’s going to be a really fun episode, very emotional, that honors 14 years of CSI.”

UPDATE: Not long after TVLine broke the news, Helgenberger celebrated by tweeting a “reunion” photo:

You know that Petersen still is an Exec Producer so gets his money,, he can’t have that many bad feelings…!!

But it’s nice to to get Marg back at least for one episode…

Not sure how they could end this show.. I know the ended L&O, Mother Ship, with just an episode.. L&O CI ended with them going out on another case though we found out this past season on SVU when Eames showed up that Goren appears to have left the force and moved away.. When the time does come to end, probably just stop.. The thing is that once they got rid of the mistake that was Langston (Fishburne) and brought in Danson to star along with Shue, it rejuvenated the show…

Good to see Catherine Willows back for a very special milestone episode of CSI. Until then, Marg Helgenberger is moving on to do Intelligence which debuts February 24th the night after the Winter Olympics.

If Grissom isn’t there—why the flashbacks? Everything is seen with Grissom’s eyes, especially for 9 seasons. And where is Grissom? Avoiding a mention of him will make it all too weird. Why can’t this show embrace its history instead of avoiding the man who made it famous?
I hope they don’t try to ‘make-up’ these actors to look younger but use actual scenes from early seasons.
And what about Warrick?
This could be a good episode, but then I remember the awful 200th episode. Cringe-worthy!

– Gary Dourdan (Warrick) will never come back : he was fired because personal issues
– William Petersen (Grissom) : He may not return as well, he critisized the show recently. He said he does not miss the show at all…

Glad Marg is returning for one episode ! I’m waiting for this one ! :)

before you think remember William Peterson is one of the producers of the show. He helps run it. He can put himself in “if” he wants. It would not be an accurate show if he is not on it. He ran the cases.

I am confused. Is Catherine only appearing in the “flashbacks”? I use to be big fan of the show back in the day. I have seen 1 or 2 episodes from last season. It just isn’t the same. I find writing and the cases to be boring.

Even though I don’t mind Elisabeth Shue, I can’t stand Finn. Everytime she is on, I have urge to put the mute button on.

That would be stupid. Why would you keep it a secret? The whole idea of having special guest appearances is to attract more viewers to the show. If they announced William Peterson was returning I guarantee the viewing audience would double. If nobody knows he’s going to be on then they won’t tune in.

Exactly! If Peterson were coming on the show not only would they NOT keep it a secret they would post it on every single entertainment news site available, put up billboards, and hire a sky writer. The idea that they would not advertise it is absurd.